Field of the Invention
The present invention relates to an ink set and an ink jet recording method using the same.
Description of the Related Art
According to an ink jet recording method, an image can be recorded (formed) on various recording media. Various inks corresponding to purposes, for example, an ink suitable for recording an image of photographic image quality on glossy paper and an ink suitable for recording a document on plain paper, have been proposed to intend better image formation. In recent years, the ink jet recording method has been utilized even in printing of a business document including characters and figures using plain paper as a recording medium, thereby increasing the frequency of its use dramatically. Therefore, the use of a pigment as a coloring material not only in a black ink but also in a color ink increases to obtain an ink suitable for recording characters and figures on a recording medium such as plain paper.
In the ink jet recording method, a general color image is recorded with three inks of a cyan ink, a magenta ink and a yellow ink, which are inks of primary colors of subtractive color mixture. What is called special (spot) color inks such as a black ink, a red ink, a green ink and a blue ink are used in addition to these inks as needed.
An image recorded with a color ink using a pigment as a coloring material involves a problem that its color developability is inferior compared with an image recorded with a color ink using a dye as a coloring material. A great number of methods for solving such a problem have been proposed. For example, there is a proposal for improving the characteristics of an image recorded on plain paper by using an ink containing a self-dispersible pigment, which is dispersible without using a dispersant, and a specific salt (Japanese Patent Application Laid-Open No. 2001-081378). In addition, there is also a proposal for improving an optical density of an image recorded by using an ink containing a self-dispersible pigment to which a functional group high in reactivity to calcium has been bonded on the basis of a calcium index which is an index of reactivity to calcium (Japanese Patent Application Laid-Open No. 2009-515007 through PCT route).